Stag Beetles

Media
photo of a male reddish-brown stag beetle
Scientific Name
About 40 species in North America north of Mexico
Family
Lucanidae (stag beetles) in the order Coleoptera (beetles)
Description

While stag beetles are not very colorful, they make up for it in pincers! Male stag beetles usually have enlarged, sometimes astonishing jaws. Most are black, brownish, or reddish brown. They are strong, elongated beetles. The antennae are enlarged at the tip or clubbed, with segments that fan open like leaves but that cannot be pressed together tightly into a ball. The antennae have 10 segments, and on many species the antennae are elbowed.

The jaws of male stag beetles are enlarged, imposing pincers that are used for fighting over females. On some species, they look like antlers (hence the name “stag beetle”). The pincers of females, though less spectacular, are still well-developed.

The larvae of stag beetles are whitish, C-shaped grubs that live in rotting wood. The heads are often brownish or black, and they have three pairs of legs. They look a lot like the larvae of scarabs and other beetles.

Common Name Synonyms
Pinching Beetles
Size
Length: from less than ½ inch to nearly 2½ inches (adults; varies with species).
Where To Find
image of Stag Beetles Distribution Map
Statewide.
Most stag beetles are found on the ground in forests. Others frequent sandy stream banks near driftwood. As with other insects, although they can go almost anywhere by foot or by wing, they tend to be near their food sources and egg-laying places. The larvae live in rotting logs, and the adults consume tree sap. In some places, stag beetle larvae have been found in deep layers of hardwood mulch used in hiking trails and playgrounds. Stag beetles are sometimes attracted to lights at night.
Larvae eat rotting wood and the juices associated with it. Adults eat tree sap where it runs after a branch or the bark has been injured. They may also eat rotting fruit, and some species apparently eat the sweet so-called honeydew secretions of aphids.
Life Cycle
Those jaws don’t just look like antlers; male stag beetles combat each other for mating opportunities just as male elk and deer do. The best mating sites are where females go to eat, or near the rotting wood where females lay eggs. Using their huge jaws, males grapple with each other for the best locations. After hatching from eggs, the larvae live in rotting wood, growing and molting, often for years. When fully grown, the larvae pupate surrounded by wood chips, then emerge as adults.

“Will it pinch me?” Maybe, if you handle it — but the jaws of males are used primarily for fighting other males, and they don’t bite people aggressively. Just about any creature with a jaw can potentially bite, and will, in defense.

The larvae are important decomposers of dead wood, which cleans up the forests and improves soil.

Several animals, including raccoons and woodpeckers, probe or poke through rotting logs and eat the grubs. Many other animals, including birds, bats, and skunks, frogs, eat the adults. Several types of flies and wasps parasitize the larvae, laying eggs on them that hatch and devour the host.
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About Land Invertebrates in Missouri
Invertebrates are animals without backbones, including earthworms, slugs, snails, and arthropods. Arthropods—invertebrates with “jointed legs” — are a group of invertebrates that includes crayfish, shrimp, millipedes, centipedes, mites, spiders, and insects. There may be as many as 10 million species of insects alive on earth today, and they probably constitute more than 90 percent all animal species.